Underground drilling involves drilling a borehole through a formation deep in the Earth using a drill bit connected to a drill string. The drill bit is typically mounted on the lower end of the drill string as part of a bottom-hole assembly (BHA) and is rotated by rotating the drill string at the surface and/or by actuation of down-hole motors or turbines. A BHA may include a variety of sensors used to monitor various down-hole conditions—such as pressure, spatial orientation, temperature, or gamma ray count—that are encountered while drilling. A typical BHA will also include a telemetry system that processes signals from these sensors and transmits data to the surface. The drilling operations may be guided through MWD data obtained from the BHA. The MWD data may be obtained by the BHA and transmitted to the surface. The MWD data can then be used to understand the formations and make plans on completion, sidetracking, abandoning, further drilling, etc.
Current MWD telemetry systems require a transmitter (typically on the BHA) and a receiver (e.g., a computer at rig with attached hardware) to have matching settings in order to engage in transmission of telemetry data. Accordingly, the settings of the transmitter on the BHA typically cannot be modified without receiving a downlinked command from the rig site. Modification of settings without the transmitter receiving the downlinked command may result in lost connection if the receiver does not recognize the change in settings. Furthermore, existing telemetry systems, especially electromagnetic (EM) based telemetry, are generally configured to transmit at higher data rates. Such higher data rates will consume more power, decreasing endurance of the BHA.
However, MWD tools are typically battery powered and can only store finite energy. Thus, improved telemetry techniques that allow for conservation of battery life and, thus, increased time before recharge, are needed.